The Anopheles gambiae sensu lato species complex consists of a number of cryptic species with different habitats and behaviours. These morphologically indistinct species are identified by chromosome ...banding. Several molecular diagnostic techniques for distinguishing between An. coluzzii and An. gambiae are still under improvement. Although, the current SINE method for identification between An. coluzzii and An. gambiae works reliably, this study describes a refinement of the SINE method to increase sensitivity for identification of An. coluzzii, An. gambiae and An. arabiensis based on amplicon dissociation curve characteristics. Field-collected samples, laboratory-reared colonies and crossed specimens of the two species were used for the design of the protocol. An. gambiae, An. coluzzii, and hybrids of the two species were sampled from Ghana and An. arabiensis from Kenya. Samples were first characterised using conventional SINE PCR method, and further assayed using SYBR green, an intercalating fluorescent dye. The three species and hybrids were clearly differentiated using the melting temperature of the dissociation curves, with derivative peaks at 72°C for An. arabiensis, 75°C for An. gambiae and 86°C for An. coluzzii. The hybrids (An. gambiae / An. coluzzii) showed both peaks. This work is the first to describe a SYBR green real time PCR method for the characterization of An. arabiensis, An. gambiae and An. coluzzii and was purposely designed for basic melt-curve analysis (rather than high-resolution melt-curve) to allow it to be used on a wide range of real-time PCR machines.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Recent outbreaks of Zika, dengue, and chikungunya have occurred in West Africa•Recently introduced Aedes albopictus is implicated in multiple arbovirus outbreaks•Arbovirus outbreaks have occurred in ...major urban centers in West Africa•Diverse factors play a role in the emergence of Aedes-borne disease in West Africa•There is urgent need for improved disease surveillance and diagnostic capacity
Arboviruses transmitted by Aedes mosquitoes are a growing global concern; however, there remain large gaps in surveillance of both arboviruses and their vectors in West Africa. We reviewed over 50 years of data including outbreak reports, peer-reviewed literature, and prior data compilations describing Zika, dengue, and chikungunya, and their vectors in West Africa. Large outbreaks of dengue, Zika, and chikungunya have recently occurred in the region with over 27,000 cases of Aedes-borne disease documented since 2007. Recent arboviral outbreaks have become more concentrated in urban areas, and Aedes albopictus, recently documented in the region, has emerged as an important vector in several areas. Seroprevalence surveys suggest reported cases are a gross underestimate of the underlying arboviral disease burden. These findings indicate a shifting epidemiology of arboviral disease in West Africa and highlight a need for increased research and implementation of vector and disease control. Rapid urbanization and climate change may further alter disease patterns, underscoring the need for improved diagnostic capacity, and vector and disease surveillance to address this evolving health challenge.
Aedes-borne disease occurrence in West Africa. Arboviral disease occurrences were extracted from previous compilations, systematic review of literature, and outbreak reports. Data are organized by timing of outbreak with panels showing oldest (bottom panel) to most recent (top panel) observations Display omitted .
Abstract
Ticks are efficient vectors for transmitting pathogens that negatively affect livestock production and pose a risk to public health. In this study,
Babesia
and
Theileria
species were ...identified in ticks collected from cattle, sheep and goats from the Kassena‐Nankana Districts of Ghana between February and December 2020. A total of 1550 ticks were collected, morphologically identified, pooled and screened for pathogens using primers that amplify a 560 bp fragment of the ssrRNA gene and Sanger sequencing.
Amblyomma variegatum
(62.98%) was the predominant tick species. From the 491 tick pools screened, 12/15 (2.44%) positive pools were successfully sequenced. The pathogen DNA identified were
Theileria ovis
in eight (15.38%) pools of
Rhipicephalus evertsi evertsi
,
Theileria velifera
in two (0.78%) pools of
A. variegatum
and
Babesia occultans
and
Babesia
sp. Xinjiang in one (1.72%) pool each of
Hyalomma truncatum
. It was further observed that
T. ovis
occurred in ticks collected from only sheep (
p
< 0.001) which were females (
p
= 0.023) and < =1 year old (
p
= 0.040). This study reports the first identification of these pathogens in ticks within Kassena‐Nankana. With the constant trade of livestock, there is a need for effective tick control measures to prevent infection spread.
Malaria vector control methods involving the use of pyrethroids remain the strategies being used against malaria vectors in Ghana. These methods include the use of long-lasting insecticidal nets and ...indoor residual spraying in many areas in Ghana. However, there is evidence that pyrethroid resistance is widespread in many areas in Ghana. Synergists have been shown to be useful in inhibiting the enzymes that are responsible for the development of resistance and hence enhance the insecticide susceptibility of Anopheles gambiae sensu lato (s.l.) in many areas. The present study investigated the effect of piperonyl butoxide (PBO) on the susceptibility status of An. gambiae s.l. across some sentinel sites in Ghana.
Three to five day old An. gambiae s.l. reared from larvae were used in WHO susceptibility tube assays. Batches of 20-25 female adult An. gambiae s.l. were exposed simultaneously to the insecticide alone and to the PBO + insecticide. The knock down rate after 60 min and mortality at 24 h were recorded.
Deltamethrin and permethrin resistance of An. gambiae s.l. was observed in all the sites in 2015 and 2016. The mortality after 24 h post exposure for deltamethrin ranged from 16.3% in Weija to 82.3% in Kade, whereas that for permethrin ranged from 3.8% in Gomoa Obuasi to 91.3% in Prestea. A significant increase in susceptibility to deltamethrin and less to permethrin was observed during both 2015 and 2016 years in most of the sites when An. gambiae s.l. mosquitoes were pre-exposed to PBO.
Findings from this study showed that the use of PBO significantly enhanced the susceptibility of An. gambiae s.l. mosquitoes in most of the sentinel sites. It is recommended that vector control strategies incorporating PBO as a synergist can be effective in killing mosquitoes in the presence of deltamethrin and permethrin resistance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In most developing countries, climate variabilities and discount rate played an integral role in the decision-making of farmers, which mostly affect their net revenue. Our study employs Ricardian ...models to empirically verify this hypothesis using data collected from three major agro-climatic zones in Ghana. We particularly estimated the comparative effect of climate change variability, discount rate, and soil fertility; due to trade-off effect of certain farm practices in response to climate change across major climatic zones and also the fact that discount rate becomes an extremely critical issue in formulating and evaluating conservation and management policy to address climate change. The result indicates that discount rate has a positive and significant effect on the farmers’ net revenue. Further, effect of changes in temperature on food crop production and hence net revenue is more felt in the forest and savannah zones. On the other hand, an increase in rainfall has significant negative effects on crop net revenues and whole-farm net revenue, but a positive effect on net revenue of farmers in the savannah zone. We also found a significant increase in soil fertility to increase crop net revenues.
Consumers are increasingly becoming very concerned about food safety, with many giving preference to organic food products over conventional food products, which make use of agrochemicals with ...potential implications for health. Furthermore, to make the food choice decisions even more complex, genetically modified (GM) foods have been introduced in an attempt to meet global food demand. Consumers therefore must make decisions regarding organic and GM foods. This paper investigates consumer heterogeneity for organic and GM tomatoes in Ghana using advanced discrete choice modelling techniques. The data for empirical application come from a choice experimental study conducted among 200 consumers in Ghana. Our econometric modelling revealed that the sampled consumers preferred organic tomatoes that are produced locally and certified by the Food and Drugs Authority. However, we find a likelihood that women and older consumers may have preferences for GM tomatoes with environmental and health benefits. Policy implications are drawn from the findings of the study.
Insecticide resistance of Anopheles gambiae (s.l.) against public health insecticides is increasingly reported in Ghana and need to be closely monitored. This study investigated the intensity of ...insecticide resistance of An. gambiae (s.l.) found in a vegetable growing area in Accra, Ghana, where insecticides, herbicides and fertilizers are massively used for plant protection. The bioefficacy of long-lasting insecticidal nets (LLINs) currently distributed in the country was also assessed to delimitate the impact of the insecticide resistance intensity on the effectiveness of those nets.
Three- to five-day-old adult mosquitoes that emerged from collected larvae from Opeibea, Accra (Ghana), were assayed using CDC bottle and WHO tube intensity assays against different insecticides. The Vgsc-L1014F and ace-1 mutations within the population were also characterized using PCR methods. Furthermore, cone bioassays against different types of LLINs were conducted to evaluate the extent and impact of the resistance of An. gambiae (s.l.) from Opeibea.
Anopheles gambiae (s.l.) from Opeibea were resistant to all the insecticides tested with very low mortality observed against organochlorine, carbamates and pyrethroid insecticides using WHO susceptibility tests at diagnostic doses during three consecutive years of monitoring. The average frequencies of Vgsc-1014F and ace-1 in the An. gambiae (s.l.) population tested were 0.99 and 0.76, respectively. The intensity assays using both CDC bottle and WHO tubes showed high resistance intensity to pyrethroids and carbamates with survivals at 10× the diagnostic doses of the insecticides tested. Only pirimiphos methyl recorded a low resistance intensity with 100% mortality at 5× the diagnostic dose. The bioefficacy of pyrethroid LLINs ranged from 2.2 to 16.2% mortality while the PBO LLIN, PermaNet
3.0, was 73%.
WHO susceptibility tests using the diagnostic doses described the susceptibility status of the mosquito colony while CDC bottle and WHO tube intensity assays showed varying degrees of resistance intensity. Although both methods are not directly comparable, the indication of the resistance intensity showed the alarming insecticide resistance intensity in Opeibea and its surroundings, which could have an operational impact on the efficacy of vector control tools and particularly on pyrethroid LLINs.
Vector population control using insecticides is a key element of current strategies to prevent malaria transmission in Africa. The introduction of effective insecticides, such as the organophosphate ...pirimiphos-methyl, is essential to overcome the recurrent emergence of resistance driven by the highly diverse Anopheles genomes. Here, we use a population genomic approach to investigate the basis of pirimiphos-methyl resistance in the major malaria vectors Anopheles gambiae and A. coluzzii. A combination of copy number variation and a single non-synonymous substitution in the acetylcholinesterase gene, Ace1, provides the key resistance diagnostic in an A. coluzzii population from Côte d'Ivoire that we used for sequence-based association mapping, with replication in other West African populations. The Ace1 substitution and duplications occur on a unique resistance haplotype that evolved in A. gambiae and introgressed into A. coluzzii, and is now common in West Africa primarily due to selection imposed by other organophosphate or carbamate insecticides. Our findings highlight the predictive value of this complex resistance haplotype for phenotypic resistance and clarify its evolutionary history, providing tools to for molecular surveillance of the current and future effectiveness of pirimiphos-methyl based interventions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tick-borne pathogens harm livestock production and pose a significant risk to public health. To combat these effects, it is necessary to identify the circulating pathogens to create effective control ...measures. This study identified
Anaplasma
and
Ehrlichia
species in ticks collected from livestock in the Kassena-Nankana Districts between February 2020 and December 2020. A total of 1550 ticks were collected from cattle, sheep and goats. The ticks were morphologically identified, pooled and screened for pathogens using primers that amplify a 345 bp fragment of the 16SrRNA gene and Sanger sequencing. The predominant tick species collected was
Amblyomma variegatum
(62.98%). From the 491 tick pools screened, 34 (6.92%) were positive for
Ehrlichia
and
Anaplasma
. The pathogens identified were
Ehrlichia canis
(4.28%),
Ehrlichia minasensis
(1.63%),
Anaplasma capra
(0.81%) and
Anaplasma marginale
(0.20%). This study reports the first molecular identification of the above-mentioned
Ehrlichia
and
Anaplasma
species in ticks from Ghana. With the association of human infections with the zoonotic pathogen
A. capra
, livestock owners are at risk of infections, calling for the development of effective control measures.
Vector bionomics are important aspects of vector-borne disease control programs. Mosquito-biting risks are affected by environmental, mosquito behavior and human factors, which are important for ...assessing exposure risk and intervention impacts. This study estimated malaria transmission risk based on vector-human interactions in northern Ghana, where indoor residual spraying (IRS) and insecticide-treated nets (ITNs) have been deployed.
Indoor and outdoor human biting rates (HBRs) were measured using monthly human landing catches (HLCs) from June 2017 to April 2019. Mosquitoes collected were identified to species level, and Anopheles gambiae sensu lato (An. gambiae s.l.) samples were examined for parity and infectivity. The HBRs were adjusted using mosquito parity and human behavioral observations.
Anopheles gambiae was the main vector species in the IRS (81%) and control (83%) communities. Indoor and outdoor HBRs were similar in both the IRS intervention (10.6 vs. 11.3 bites per person per night b/p/n; z = -0.33, P = 0.745) and control communities (18.8 vs. 16.4 b/p/n; z = 1.57, P = 0.115). The mean proportion of parous An. gambiae s.l. was lower in IRS communities (44.6%) than in control communities (71.7%). After adjusting for human behavior observations and parity, the combined effect of IRS and ITN utilization (IRS: 37.8%; control: 57.3%) on reducing malaria transmission risk was 58% in IRS + ITN communities and 27% in control communities with ITNs alone (z = -4.07, P < 0.001). However, this also revealed that about 41% and 31% of outdoor adjusted bites in IRS and control communities respectively, occurred before bed time (10:00 pm). The mean directly measured annual entomologic inoculation rates (EIRs) during the study were 6.1 infective bites per person per year (ib/p/yr) for IRS communities and 16.3 ib/p/yr for control communities. After considering vector survival and observed human behavior, the estimated EIR for IRS communities was 1.8 ib/p/yr, which represents about a 70% overestimation of risk compared to the directly measured EIR; for control communities, it was 13.6 ib/p/yr (16% overestimation).
Indoor residual spraying significantly impacted entomological indicators of malaria transmission. The results of this study indicate that vector bionomics alone do not provide an accurate assessment of malaria transmission exposure risk. By accounting for human behavior parameters, we found that high coverage of ITNs alone had less impact on malaria transmission indices than combining ITNs with IRS, likely due to observed low net use. Reinforcing effective communication for behavioral change in net use and IRS could further reduce malaria transmission.
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